The Genomic Walking strategy is currently the only sequencing method sensitive to methylation patterns and thus should be used to detect methylated residues. The current implementation of the GW strategy is limited by the sensitivity of the autoradiography used to image the sequencing blots (about 10[-17] moles per sequencing band). The use of a spatially resolving MPD system (that has a proven resolution of 10[-20] moles) to resolve the sequencing ladders produced by the GW strategy would allow the survey of the methylation patterns as well as the analysis of sequence of genes in linkage analysis. There are one instrumental and one biochemical objective that we plan to address in this proposal: * development of multilabel imager with spatial resolution better than 100 microns and sensitivity of 10[-20] moles; * imaging human genomic sequencing blots to identify methylated residues and determine the dynamic range of the methylation patterns.